The invention relates to a chemically adsorbed film and method of manufacturing the same; more particularly, the invention relates to a chemically adsorbed film and its method of manufacture, in which the molecules are, as a whole, densely connected to the substrate surface by chemically bonding graft molecules to chemically adsorbed stem molecules.
Conventional methods used for manufacturing chemically adsorbed film include the procedure mentioned, for example, on page 92, volume 102 of the Journal of American Chemical Society (J. Sagiv et al., Journal of American Chemical Society, 92, 102 (1980)) and page 851 of the sixth volume of Langmuir (K. Ogawa et al., Langmuir, 6, 851 (1990)). In this method, a chemically adsorbed film is manufactured by a dehydrochlorination reaction between groups exposed on a substrate surface, such as dehydroxyl groups, and a chlorosilane-based surface active material. The adsorption reaction is carried out for many hours until it reaches the point of saturation adsorption. To form one chemically adsorbed film, an adsorption reaction, a washing and a rinsing are performed once.
However, the above-noted method is limited in improving film density; the number of functional groups of the group itself sets an upper limit on the site number for the adsorption reaction of chemically adsorbed material. As a result, based on the above-noted method, there is a problem that film density can not be improved even by significantly lengthening the time for adsorption reaction.
The method of building up chemical admolecules on a chemically adsorbed film (U.S. Pat. Nos. 4,673, 4,992,300) is also known as a conventional method. However, it is difficult to increase the density of molecules on the substrate surface using this method.
An objective of the invention is to provide a chemically adsorbed film with improved film density, while detailing its method of manufacture, thereby solving the above-noted problems.
To accomplish the above objective, the chemically adsorbed film of this invention is formed by a direct or indirect covalent bonding of stem molecules to the substrate surface via at least one element chosen from Si, Ge, Sn, Ti, Zr, S or C. Graft molecules are covalently bonded to at least one element chosen from Si, Ge, Ti, Zr, S or C via at least one bond chosen from xe2x80x94SiOxe2x80x94, xe2x80x94GeOxe2x80x94, xe2x80x94SnOxe2x80x94, TiOxe2x80x94, ZrOxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94SOxe2x80x94and xe2x80x94Cxe2x80x94.
In the above-noted composition, it is preferable that direct or indirect covalent bonding between stem molecules and the substrate surface employs at least one bond chosen from the following: xe2x80x94SiOxe2x80x94,xe2x80x94SiNxe2x80x94, xe2x80x94GeOxe2x80x94, xe2x80x94GeNxe2x80x94, xe2x80x94SnOxe2x80x94, xe2x80x94SnNxe2x80x94, xe2x80x94TiOxe2x80x94, xe2x80x94TiNxe2x80x94, xe2x80x94ZrOxe2x80x94and xe2x80x94ZrNxe2x80x94.
In the above-noted composition, it is preferable that a stem or graft molecule contains a hydrocarbon chain, a fluorocarbon chain, an aromatic group or a heterocyclic group.
In the above-noted composition, it is preferable that an unsaturated bond is included in a stem or graft molecule.
In the above-noted composition, it is preferable that a chemically adsorbed film is a monomolecular chemically adsorbed built-up film.
The method of manufacturing a chemically adsorbed film of the invention, which is the method of bonding graft molecules to stem molecules, comprises the following procedures:
(1) directly or indirectly contacting the chemical admolecules, containing functional groups as shown in formula [A] or formula [B] at the end of molecules, with the substrate surface, which either has or is given an active hydrogen or alkali metal on the surface, thereby covalently bonding the chemical admolecules, stem molecules, to the substrate surface by condensation reaction;
removing unreacted chemical admolecules;
reacting the substrate surface with water, thereby substituting the halogen or alkoxyl group, or both, to a hydroxyl group.
Formula [A] is provided as seen below:
xe2x80x94AXm 
where X represents halogen, A represents Si, Ge, Sn, Ti, Zr, S or C, m represents 2 or 3.
Formula [B] is represented by:
xe2x80x94A(Q)m 
where Q represents an alkoxyl group, A represents Si, Ge, Sn, Ti, Zr, S or C, m represents 2 or 3.
The method additionally comprises contacting the substrate surface with chemical admolecules containing at least one functional group at the end of molecules, chosen from formulas [C] through [G], thereby creating a condensation reaction;
removing unreacted chemical admolecules;
reacting the substrate surface with water.
Formula [C] is designated:
xe2x80x94AXn 
where X represents halogen, A represents Si, Ge, Sn, Ti, Zr, S or C, n represents 1, 2 or 3.
Formula [D] is designated:
xe2x80x94A(Q)n 
where Q represents an alkoxyl group, A represents Si, Ge, Sn, Ti, Zr, S or C, n represents 1, 2 or 3.
Formula [E] is designated:
xe2x80x94SO2X 
where X represents halogen.
Formula [F] is represented by:
xe2x80x94SOX 
where X represents halogen.
Formula [G] is denoted by:
 greater than Nxe2x80x94CHO or xe2x80x94OCHO 
In the above-noted composition, it is preferable that unreacted chemical admolecules are removed by a nonaqueous solution.
In the above-noted composition, it is preferable that either liquid water or steam is used in the process of reacting stem or graft molecules with water.
In the above-noted composition, it is preferable that the chemical adsorbent, which contains trichlorosilane-based ends, is used as stem or graft molecules.
In the above-noted composition, it is preferable that the condensation reaction due to the contact with stem or graft molecules is a dehydrochlorination, alcohol elimination or water elimination reaction.
In the above-noted composition, it is preferable that a hydrocarbon chain, a fluorocarbon chain, an aromatic group or a heterocyclic group is included in stem or graft molecules.
In the above-noted composition, it is preferable that an unsaturated bond is included in stem or graft molecules.
Based on this invention, the density of a chemically adsorbed film is improved by increasing the number of admolecules. More specifically, the number of admolecules can be increased by the rise in the site number, which is promoted by introducing graft molecules to the roots of stem molecules. In addition, it is possible that graft molecules are directly bonded to the substrate.
Based on the preferable composition of the invention, direct or indirect covalent bonding of stem molecules to the substrate surface employs at least one bond chosen from xe2x80x94SiOxe2x80x94, xe2x80x94SiNxe2x80x94, xe2x80x94GeOxe2x80x94, xe2x80x94GeNxe2x80x94, xe2x80x94SnOxe2x80x94, xe2x80x94SnNxe2x80x94, xe2x80x94TiOxe2x80x94, xe2x80x94TiNxe2x80x94, xe2x80x94ZrOxe2x80x94 and xe2x80x94ZrNxe2x80x94, thus allowing a molecular adsorption film to become chemically stable.
In a preferable composition of the inventionxe2x80x94with an unsaturated bond in the hydrocarbon chain of stem or graft moleculesxe2x80x94it is possible to polymerize stem and/or graft molecules or to introduce another molecule after the formation of a chemically adsorbed film. It is preferable that the unsaturated bond is the double bond of carbonxe2x80x94carbon (Cxe2x95x90C), the double bond of carbon-nitrogen (Cxe2x95x90N), the triple bond of carbonxe2x80x94carbon (Cxe2x89xa1C), the triple bond of carbon-nitrogen (Cxe2x89xa1N) or the like.
Furthermore, a preferable composition of the invention is a chemically adsorbed film and a monomolecular chemically adsorbed built-up film, whereby a film with increased molecular density is formed.
In the method of manufacturing a chemically adsorbed film of the invention, said film with improved film density efficiently may be formed by increasing the number of admolecules, which is made possible by increasing the site number. Moreover, this method can reduce the reaction time.
According to a preferable composition of the invention, the unreacted chemical admolecules are removed by a nonaqueous solution, and a film with a thickness at an angstrom or nanometer level is uniformly formed over the substrate surface.
In a preferable composition of the invention, stem or graft molecules are reacted with liquid water or steam, a halogen atom can be substituted for a hydroxyl group quite efficiently.
The above-noted method of using the chemical adsorbent with trichlorosilane ends as the stem or graft molecules is quite practical, providing a high adsorption reaction.
A preferable composition of the present invention comprises a condensation reaction due to the contact with stem or graft molecules in a dehydrochlorination, alcohol elimination or water elimination reaction, whereby a high reaction rate is possible.